This related to calibration, and more particularly, to calibration of wireless communications circuitry in electronic devices.
Electronic devices such as portable computers and cellular telephones are often provided with wireless communications capabilities. For example, electronic devices may use long-range wireless communications circuitry such as cellular telephone circuitry to communicate using cellular telephone bands at 700 MHz, 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, and 2100 MHz. Electronic devices may use short-range wireless communications circuitry to handle communications with nearby equipment. For example, electronic devices may communicate using the WiFi® (IEEE 802.11) bands at 2.4 GHz and 5 GHz and the Bluetooth® band at 2.4 GHz.
Wireless communications circuitry often includes a power amplifier that amplifies an electronic input signal to produce an amplified electronic output signal having more power than the input signal. The ratio of power of the output signal to the power of the input signal is commonly referred to as the gain of an amplifier. Power amplifiers commonly suffer from a non-linear gain in which a high power input signal is not amplified as much as a low power input signal (i.e., the gain is reduced for high power signals), and in which the phase of the output signal changes as a function of the input power. To compensate for this and other distortions of a signal by a power amplifier, wireless communications circuitry often includes a pre-distortion compensator circuit that alters an input signal to the power amplifier such that the output of the power amplifier is linear (i.e., the signal gain is the same) for a broader range of input signal powers. Pre-distortion compensator circuits take, as inputs, pre-distortion coefficients based on measured performance of the power amplifier.
In order to provide electronic devices that perform uniformly across all devices, each electronic device may be calibrated during manufacturing before delivery to end users. Calibration operations include determination of pre-distortion coefficients by measuring the performance of wireless communications power amplifiers in each device. Measuring the performance of power amplifiers in each electronic device can be time consuming and can therefore slow the pace of production of the devices and can increase the cost of productions.
It would therefore be desirable to provide improved calibration systems for electronic devices with wireless communications capabilities.